Has anyone used these before? Any comments?

The TR Series Retrofit Lighting Relays are magnetically latching type devices with a built-in transformer for low voltage control of lighting circuits. Designed to mount in existing junction or pull boxes, these units can be connected to provide master sweep-off and sweep-on control of lighting while existing line voltage switches and wiring remain in place for local on/off and override functions. Low voltage inputs require momentary contact closures (SPDT for on/off control, SPST for off control only) and may be combined up to 40 per phase within Class 2 wiring limits. Relay contacts are 20A normally open and can switch up to a 1 hp motor load. This unique technology, which allows a single coil to serve as both a transformer secondary and a relay operator, results in a compact and economical package for both retrofit and new installations.

Yeah, that looks like an Amp low voltage relay for lighting. Here in NJ back in the 60's, many electrical contractors (EC) would install these low voltage (LV) relays in the attic. Then at every door there was a LV switch to turn on the lights. You could have 1-5 switches at any point in the house. You could control any/all of the outside lights from any spot in the house. I must have seem real high tech at the time.

Although not exactly them same, we use the heck out of LV relay "switch packs" in conjunction with ceiling mtd. occupancy sensors. This is done generally in office spaces. The looks and functions are almost identical.
Like Harold said, "Touchplate" systems and the like have been around a long time.
(GE still uses the same relays in their lighting controls as they did 40 yrs. ago)

Now, that is a great idea, I wish we could get them over here in NZ.
Would save a lot of headaches with lighting control.